Determination of Lead, Cadmium, Zinc, Copper, and Iron in Foods by Atomic Absorption Spectrometry after Microwave Digestion: NMKL1 Collaborative Study

Abstract

A method for determination of lead, cadmium, zinc, copper, and iron by atomic absorption spectrometry (AAS) after microwave digestion was subjected to a collaborative study in which 16 laboratories participated [including users of inductively coupled plasma (ICP) and ICP–mass spectrometry (MS)]. The types of samples included in the study were minced fish, wheat bran, milk powder, bovine and pig liver, mushroom, 2 simulated diets, and bovine muscle; the last 4 were certified reference materials. These were analyzed as single (4 samples), double blind (1 sample), or split level (2 samples) samples. Before the collaborative study, a pretrial was conducted in which 4 ready-made solutions and one fish tissue sample were analyzed for Pb and Cu. The reproducibility relative standard deviation (RSDR) values, for results above the detection limit, ranged from 59% at 0.155 mg/kg to 16% at 1.62 mg/kg for Pb, from 28% at 0.0124 mg/kg to 11% at 0.482 mg/kg for Cd, from 9.3% at 35.3 mg/kg to 1.7% at 147 mg/kg for Zn, from 39% at 0.241 mg/kg to 3.0% at 63.4 mg/kg for Cu, and from 17% at 7.4 mg/kg to 5.9% at 303 mg/kg for Fe. The RSDR values agreed well with the norms described by the International Union of Pure and Applied Chemistry. As a complement to the AAS determinations, a number of laboratories analyzed the samples either by ICP or by ICP–MS. The results of these analyses agreed well with the AAS results. On the basis of the results of the collaborative study, the method was adopted Official First Action by AOAC INTERNATIONAL.

Comparison of the nutritional composition of experimental fermented milk:wheat bulgur blends and commercially available kishk and tarhana products

“…Quantification of calcium, iron, zinc and magnesium was conducted based on AOAC method 999.11 (Jorhem & Engman, 2000). Briefly, each sample (1g) was dry-ashed by placing at 500°C in a muffle furnace for 4 hrs.…”

Bioaccumulation of zinc ions in Lactobacillus rhamnosus B 442 cells under treatment of the culture with pulsed electric field

“…The obtained solutions were cooled down, transferred to 25 mL measuring flasks, and topped up with deionised water. Concentration of zinc ions in L. rhamnosus B 442 cells was determined using an electrothermal atomic absorption spectrophotometer (ET-AAS, VARIAN AA 280 FS) according to Jorhem and Engman [29] in an accredited laboratory (validation parameters: precision 5.1%, extended uncertainty 14%). The determination was performed in triplicate.…”

Optimization of spray-drying conditions for the preparation of whey protein concentrate–iron complex using response surface methodology

“…The iron content of the complex prepared at the optimized condition was estimated by utilizing the dry digestion method. [18] A standard curve was prepared using ferrous sulfate heptahydrate salt. Sample 100 mgwas weighed in a silica crucible and ashed at 550°C for 8 h. Ten milliliters of triple acid (nitric acid:perchloroacetic acid:sulphuric acid: 3:2:1) was added to ash and heated on the hot plate for its complete dissolution.…”